UNSTEADY FACTORS AFFECTING SALT DIFFUSION IN THE STRATIFIED FLOW SYSTEM AT A RIVER MOUTH

影响河口层流系统盐分扩散的不稳定因素

基本信息

批准号：
04452231
负责人：
YOSHIDA Shizuo
金额：
$ 3.26万
依托单位：
Hokkaido University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1992
资助国家：
日本
起止时间：
1992 至 1994
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-04452231/
关键词：
River Mouth Stratified Flow Two-Layr Flow Salt Diffusion Salt Wedge Entrainment Coefficient Interfacial Instability 界面不安定多層流界面波

项目摘要

The problem of salt diffusion in highly stratified flows such as those found at the mouth of a river is vital to considerations of agriculture and fisheries. Placement and control of the gates governing extraction of fresh water from a river have become social issues. Previous research has assumed that these flows are steady, and has focussed on problems of shear instability in the vicinity of the interface and natural turbulence. The research described below has examined these flows from the practical standpoint of whether and to what extent unsteady factors such as atmospheric pressure, tide, river flowrate, and wind affect salt diffusion around the river mouth. Those results have been used to attempt to develop an expression for improving predictions of the salinity of the river surface at any given point and time.These studies have been carried out mainly in the lower basin of the Ishikari River, Hokkaido, which is typical of a highly stratified flow. Observations were carried out … More in the summers of 1992,1993 and 1994 for about two months each. The observation methods were improved year by year and enough qualitative and quantitative data have been taken to fulfilll the research goals described above. The results of our research are as follows :1) Wind is the dominant factor in the surface salinity of a river. 2) The average entrainment coefficient of the salt wedge is given by the following formula : E = 1.92 * 10^<-6>e^<0.405^^W> for 118m^3/sec, E =2.24*10^<-6>e^<0.281^^W> for 146m^3/sec 3) The process of diffusion of salt from the salt wedge to the surface of a river has been shown to be the following : Wind blows>waves are generated>the turbulence in the upper layr increases>the distribution of salt in the upper layr is rendered uniform>the density gradient around the interface increases>the salt diffusion across the interface increases>the surface salinity increases. 4) The time average profiles of the flow system are stable throughout almost the entirity of the stratified flow system. 5) The process of diffusion is accelerated by an increase in river flowrate, but the salinity of the river water flow itself decreases. 6) Bridge piers and protuberences in the river bottom cause great disruptions in the interface, but the effect of these disruptions on salt diffusion is localized. 7) In order to predict the present surface salinity at any location it is sufficient to have an hourly record of wind speed along the river course and the discharge rate. Less

高度分层流的盐扩散问题，例如在阿斯科群岛的口中发现的盐分以及对从河流中提取淡水提取的大门的位置和控制已成为社会化。在下面描述的界面和湍流的界面中的不稳定性研究了是否和哪些exphere液因子，潮汐，潮汐，河流流量和风能影响盐分的盐分的预测。在任何给定的时间和时间上，这些研究主要是在Ishikari河的下盆地中进行的，这是典型的993和1994年。 WS的足够定性和实现。对于146m^3/sec 3/sec的118m^3/sec 3）盐从河表面扩散的过程是要吹动>波是>波的> nere>上层的urber脉增加>在上固定的界面>界面>盐分扩散在界面> 3）流量系统的平均剖面几乎是分层流量系统的诱因。河流流量的增加，但河流流量流量的盐度加速了6）桥梁和河底的桥梁，导致界面发生了很大的干扰，但是这些干扰对盐扩散的影响是沿着河流的风速和迪斯科速度的速度。